CN115230363A - Optical anti-counterfeiting element, design method thereof and anti-counterfeiting product - Google Patents
Optical anti-counterfeiting element, design method thereof and anti-counterfeiting product Download PDFInfo
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Abstract
The embodiment of the invention provides an optical anti-counterfeiting element, a design method thereof and an anti-counterfeiting product, and belongs to the technical field of anti-counterfeiting. The optical anti-counterfeiting element is provided with a smooth diffuse reflection curved surface, and incident light can form uniform brightness distribution in a range not less than a preset observation angle set omega v after being reflected by the diffuse reflection curved surface; the diffuse reflection curved surface comprises a modified curved surface area and an unmodified curved surface area, the modified curved surface area and the unmodified curved surface area have different reflection characteristics, and the modified curved surface area corresponds to a pattern area of the animation frame; when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface areas jointly present patterns of dynamic characteristics, and the unmodified curved surface areas jointly present a background of the dynamic characteristics. The manufacturing process is simple, and dynamic characteristics such as color and/or light and shade contrast can be flexibly realized.
Description
Technical Field
The invention relates to the technical field of anti-counterfeiting, in particular to an optical anti-counterfeiting element, a design method thereof and an anti-counterfeiting product.
Background
In order to prevent counterfeiting by means of scanning, copying and the like, optical anti-counterfeiting technology is widely adopted in various high-security or high-value-added products such as bank notes, financial bills and the like, and a very good effect is achieved.
Currently, the technology of interest is the combination of a microstructure determined by plate making and an optically variable layer, as disclosed in chinese patents CN 102712207A and CN 107995894A, and the brightness distribution of reflected light is modulated by a pre-designed micro-reflective surface to achieve a dynamic effect, and the combination of color change and dynamic effect can be achieved by superimposing an interference coating. This can often produce a variety of motion effects in patterns such as lines, circles, curves or text, and can produce a three-dimensional perspective. However, in most cases, the color and the hue of the pattern and the background are only the same, and the contrast relationship between light and shade is basically single, so that it is difficult to realize the dynamic characteristics of various colors or any relation between light and shade.
A display with three-dimensional depth effect can also be produced by a moire magnification configuration based on microlenses and micro patterns, as described for example in patent WO 2005/052650 A2. Here, a periodic presentation composed of many small micropatterns is magnified with a grid composed of microlenses having similar but not identical periods. In this way, a stereoscopic impression can be produced that is clearly in front of or behind the actual surface, or so-called orthogonal parallax motion can be produced. However, such a moir e magnification configuration is disadvantageous in that it is complicated to manufacture, requires two embossing steps for the microlenses and the micropattern, and requires precise alignment between the two steps.
Finally, as described for example in patent WO2014/108303A1, the magnetically aligned reflective pigments are aligned with correspondingly shaped magnets, thereby creating a bright (especially ring-shaped) dynamic effect that may include a certain depth effect. The effect is very bright and easily visible, but the required magnetic ink is expensive and the kind and resolution of the effect is limited by the available magnets and is difficult to adjust at will.
In addition to the disadvantages listed above, the above inventions employ structures in the form of "cells", such as micro-reflectors, flakes, microlens cells, abrupt changes in slope and voids between cells inevitably result in an inability to adequately represent the display area of the element and reduce the resolution of the image. Therefore, it is necessary to develop an optical security element having a sufficient level of expression, a simple manufacturing process, and a flexible dynamic characteristic such as color and/or contrast.
Disclosure of Invention
The embodiment of the invention aims to provide an optical anti-counterfeiting element, a design method thereof and an anti-counterfeiting product, wherein the optical anti-counterfeiting element is simple in manufacturing process and can flexibly realize dynamic characteristics such as color and/or light-dark contrast.
In order to achieve the above object, an embodiment of the present invention provides an optical security element, which is capable of presenting a dynamic feature, where the dynamic feature is pre-designed as a reproduction of a set of animation frames visible at a preset viewing angle set Ω v, and each animation frame includes a pattern area and a background area forming an optical contrast with the pattern area; the optical anti-counterfeiting element is provided with a smooth diffuse reflection curved surface, and incident light can form uniform brightness distribution in a range not less than the preset observation angle set omega v after being reflected by the diffuse reflection curved surface; the diffuse reflection curved surface comprises a modified curved surface area and an unmodified curved surface area, the modified curved surface area and the unmodified curved surface area have different reflection characteristics, and the modified curved surface area corresponds to the pattern area; when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface areas jointly represent the pattern of the dynamic feature, and the unmodified curved surface areas jointly represent the background of the dynamic feature.
Optionally, the diffusely reflective curved surface is periodic in at least one direction.
Optionally, the diffusely reflective curved surface is non-periodic in at least one direction.
Optionally, the average distance between adjacent peaks and valleys of the diffusely reflective curved surface is from 5 μm to 100 μm, preferably from 10 μm to 30 μm.
Optionally, an average height difference between adjacent peaks and valleys of the diffusely reflective curved surface is 1 μm to 10 μm.
Optionally, at least a portion of the unmodified region is smooth or has a secondary structure.
Optionally, the modified region is modified by one or more of the following ways: adding a secondary structure to the modified region; smoothing the modified region; flattening the modified area; arranging the modified region to have a protrusion or a depression compared to the unmodified region; adjusting the angle of the modified area so that the incident light is reflected to a range beyond the preset observation angle set omega v; or the thickness of the plating or coating of the modified region is adjusted to be different from the unmodified region.
Optionally, in the case that the modified region is modified by two or more of the plurality of ways, the two or more ways exist in a parallel combination and/or a serial combination.
Optionally, the secondary structure has a lateral feature size of 0.2 μm to 5 μm.
Optionally, the modified region has a width of 0.5 μm to 20 μm, preferably 2 μm to 10 μm.
Optionally, the different reflection characteristics refer to that the modified region and the unmodified region have one or a combination of different reflection colors, different reflection brightnesses, or different reflection textures when irradiated by the incident light.
Correspondingly, the embodiment of the invention also provides a design method for the optical anti-counterfeiting element, which comprises the following steps: designing a dynamic feature, wherein the dynamic feature is a reproduction of a group of animation frames visible at a preset observation angle set omega v, and each animation frame comprises a pattern area and a background area forming optical contrast with the pattern area; designing a smooth diffuse reflection curved surface for the optical anti-counterfeiting element, so that incident light can form uniform brightness distribution in a range not less than the preset observation angle set omega v after being reflected by the diffuse reflection curved surface; modifying regions corresponding to the pattern regions of the animation frames to form modified curved surface regions based on the observation angles of the animation frames of the group of animation frames, so that the modified regions and the unmodified curved surface regions have different reflection characteristics, when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface regions jointly represent the patterns of the dynamic features, and the unmodified curved surface regions jointly represent the background of the dynamic features.
Optionally, the diffusely reflective curved surface is periodic in at least one direction.
Optionally, the diffusely reflective curved surface is non-periodic in at least one direction.
Optionally, the average distance between adjacent peaks and valleys of the diffusely reflective curved surface is from 5 μm to 100 μm, preferably from 10 μm to 30 μm.
Optionally, an average height difference between adjacent peaks and valleys of the diffusely reflective curved surface is 1 μm to 10 μm.
Optionally, modifying, based on the viewing angle of each animation frame of the group of animation frames, a region corresponding to the pattern region of each animation frame to form a modified curved surface region, including: pixelating each animation frame of the set of animation frames and the diffuse reflective surface; determining a first azimuth angle and a first pitch angle of each animation frame, the first azimuth angle and the first pitch angle being determined according to an observation angle of the animation frame; determining a second azimuth angle and a second pitch angle of each pixel of the diffuse reflection curved surface, wherein the second azimuth angle and the second pitch angle are determined according to a normal vector of the pixel of the diffuse reflection curved surface; for each animation frame of the set of animation frames, performing the steps of: finding pixels corresponding to a second azimuth angle and a second pitch angle which are matched with the first azimuth angle and the first pitch angle of the animation frame at positions of the diffuse reflection curved surface corresponding to pixels of the pattern area in the animation frame, so as to form an area corresponding to the pattern area of the animation frame in the diffuse reflection curved surface; and modifying an area formed in the diffusely reflective curved surface corresponding to a pattern area of the animation frame.
Optionally, finding, at a position of the diffuse reflection curved surface corresponding to a pixel of a pattern region in the animation frame, a pixel corresponding to a second azimuth angle and a second pitch angle that are matched with the first azimuth angle and the first pitch angle of the pixel of the pattern region, includes: and searching pixels corresponding to a second azimuth angle of which the angle difference between one half of the first azimuth angle is within a first preset angle difference range and a second pitch angle of which the angle difference between the other half of the first azimuth angle is within a second preset angle difference range within a preset distance range between the diffuse reflection curved surface and pixels of a pattern area in the animation frame.
Optionally, the preset distance range indicates that a distance between the preset distance range and a position where a pixel of the pattern region in the animation frame is located is less than 100 μm, and preferably less than 50 μm; and/or said first predetermined angular difference range is an angular difference of less than 3 °, preferably less than 0.5 °, from said first azimuth angle; and/or said second predetermined angular difference range means an angular difference of less than 3 °, preferably less than 0.5 °, from said first pitch angle.
Optionally, modifying the region corresponding to the pattern region of each animation frame to form a modified curved surface region includes performing one or more of the following manners: adding a secondary structure to the modified region; smoothing the modified region; flattening the modified area; arranging the modified region to have a protrusion or a depression compared to the unmodified region; adjusting the angle of the modified region so that the incident light is reflected to a range beyond the preset set of viewing angles Ω v; or the thickness of the plating or coating of the modified region is adjusted to be different from the unmodified region.
Optionally, the dynamic characteristics are one or a combination of translation, rotation, scaling, deformation, hiding and yin-yang conversion; and/or the optical contrast is one or the combination of different colors, different brightness, different texture and the like which are visible to human eyes.
Optionally, the modified region has a width of 0.5 μm to 20 μm, preferably 2 μm to 10 μm.
Correspondingly, the embodiment of the invention also provides an anti-counterfeiting product using the optical anti-counterfeiting element.
Correspondingly, the embodiment of the invention also provides a data carrier, and the data carrier is provided with the optical anti-counterfeiting element or the anti-counterfeiting product.
The optical anti-counterfeiting element provided by the embodiment of the invention has a simple manufacturing process, can flexibly realize dynamic characteristics such as color and/or light-dark contrast, and the like, can present various multicolor dynamic characteristics in a macroscopic view, and does not have directly recognizable arrangement rules in a microscopic view, so that the counterfeiting difficulty is enhanced in multiple dimensions such as microstructure design, a manufacturing process and the like.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings, the illustrations are not drawn to scale for clarity. In the drawings:
FIG. 1 is a schematic view of diffuse reflection of incident light by a diffuse reflective curved surface area of an optical anti-counterfeiting element;
FIG. 2 is a design example of a periodic diffuse reflective curved area;
FIG. 3 is an exemplary design of an aperiodic diffusely reflecting curved surface region;
FIG. 4 is an embodiment of determining a region of a surface to be modified based on an animation frame;
FIG. 5 is another embodiment of determining a region of a surface to be modified based on an animation frame;
FIG. 6 is a schematic view of a partial or entire modification of a modified curved surface region;
figure 7 is a schematic representation of the use of an optical security element on a banknote.
Detailed Description
The following describes in detail embodiments of the present invention with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.
The embodiment of the invention provides an optical anti-counterfeiting element, which can present dynamic characteristics, wherein the dynamic characteristics are designed in advance as a group of reappearance of animation frames visible at a preset observation angle set omega v, and each animation frame comprises a pattern area and a background area forming optical contrast with the pattern area; the optical anti-counterfeiting element is provided with a smooth diffuse reflection curved surface, and incident light can form uniform brightness distribution in a range not less than the preset observation angle set omega v after being reflected by the diffuse reflection curved surface; the diffuse reflection curved surface comprises a modified curved surface area and an unmodified curved surface area, the modified curved surface area and the unmodified curved surface area have different reflection characteristics, and the modified curved surface area corresponds to the pattern area; when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface areas jointly represent the patterns of the dynamic characteristics, the unmodified curved surface areas jointly represent the background of the dynamic characteristics, that is, the modified reflection surface elements jointly represent the patterns of the dynamic characteristics, and the unmodified reflection surface elements jointly represent the background of the dynamic characteristics.
The different reflection characteristics refer to that the modified area and the unmodified area have one or a combination of different reflection colors, different reflection brightness or different reflection textures when the incident light irradiates.
When the diffuse reflection curved surface is irradiated by incident light, the animation frame can be observed under the observation angle corresponding to each animation frame, wherein the pattern of the observed animation frame is represented by the modified curved surface area, and the background of the observed animation frame is represented by the unmodified curved surface area.
The group of animation frames visible at the preset observation angle set omega v in the embodiment of the invention refers to that the observation angles correspond to the animation frames one by one, and one observation angle corresponds to one animation frame.
The dynamic characteristics of the embodiment of the invention substantially refer to dynamic characteristics appearing when the observation angle is changed. In principle, the viewing angle may be the angle of one or more of the three elements of the light source (i.e. incident light), the element and the viewer. For example, under the condition that the positions of the illumination light source and human eyes are not changed, the optical anti-counterfeiting element or the article with the optical anti-counterfeiting element is held in the hand, and the designed dynamic characteristic can be seen by shaking the element back and forth or left and right, namely changing the angle of the optical anti-counterfeiting element. For simplicity of description, the viewing direction, and hence the viewing angle, is defined by the line connecting the eye of the viewer and the point of view. It should be noted that this definition does not materially affect or limit any of the concerns of the embodiments of the present invention. The observation angle is a three-dimensional space parameter, so that the observation angle needs to be decomposed into at least two angles for accurate description. For example, pitch and azimuth angles can be used together, and the angles between the observation direction and three coordinate axes of x, y and z can also be used together.
The pattern of the animation frame may be designed as letters, numbers, characters, symbols or geometric shapes (especially circles, ovals, triangles, rectangles, hexagons or stars, etc.). The above dynamic characteristics generally refer to any one of translation, rotation, scaling, deformation, hiding, yin-yang transformation, and the like of a design pattern presented by an element and directly visible to human eyes, and may also be any combination of these dynamic characteristics. The translation may be designed to translate the design in a particular direction, or may be designed to translate in multiple directions, the directions of translation being associated with the viewing direction. One commonly used combination feature is that while the position of the designed animation frame pattern changes, its shape also changes, such as the circle changes to a square. The dynamic characteristics can have orthogonal parallax motion behaviors of the patterns, namely the motion direction of the patterns is always vertical to the change of the observation direction, and the attention of an observer is further attracted through an anti-intuitive phenomenon. The motion of the animated frame pattern can create a stereoscopic impression floating above or below the plane of the element by the principle of binocular horizontal parallax. The pattern may also comprise a plurality of sub-patterns exhibiting the same or different motion behaviour and/or the same or different floating height or floating depth. In particular, the pattern may comprise at least a first curve and a second curve, which curves, when viewed from a first or second viewing direction, respectively, appear as a first or second target curve, respectively, located at a central position of the first or second area. The two curves preferably move in different (preferably opposite) directions when the security element is tilted, thereby creating a particularly dynamic appearance. It will be appreciated that in the same way the pattern of the security element may also comprise more than two curves, which curves may move in the same or different directions when the security element is tilted. For example, a curve in the form of an alphanumeric string may alternately exhibit different motion behavior, such as alternately floating above or below the plane of the planar pattern area, and moving according to its floating height when tilted. Specific principles of various dynamic characteristics can be referred to in the prior patent texts CN 102712207A, CN 107995894A, WO 2005/052650 A2 and the like. The terms "pattern" and "pattern area" may be substituted for each other in the embodiments of the present invention.
The dynamic characteristics can be represented by a group of pictures generated by computer software, such as mathematical computation software, pattern processing software and the like during specific design. For example, using a bitmap in the format bmp, different colored design patterns and a common background of the patterns are represented by gray values of 0-255. Each picture corresponds to visual information presented to human eyes under a specific observation angle, and is called a frame of animation of designed dynamic characteristics.
The observation angle set Ω v means that all preset dynamic characteristics can be seen when the observation angle of human eyes changes in the set. The optical security element may reflect illumination beyond the collection, but such reflected light may not be associated with the designed animation feature, and may also provide darker or black visual information for the animated feature. The set of viewing angles Ω v may be described in terms of azimuth and elevation angles, for example, the azimuth angle may be designed to be 0-360 °, the elevation angle may be 0-35 ° or 10-50 °, etc., i.e. the dynamic features may be seen in the area where the human eye is in the cone shape. The setting of the angle parameter depends on the purpose of the designer, the owned lighting environment of the observer, the observation habit, and the like.
The diffusely reflective curved S-region may use the pitch and azimuth angles to determine the orientation of the curved region throughout. Of course, other parameters may be used to determine the orientation of the surface region, particularly parameters that are orthogonal to each other, such as two orthogonal components of the direction of the surface region. To produce sufficiently fine patterns and continuously varying dynamic features, the length of the undulating features of the diffusely reflective curved surface S, i.e., the average distance between adjacent peaks and valleys, is preferably less than the discrimination capability at the human eye, which is typically about 100 μm at photopic distances, which improves the resolution capability at closer distances. Therefore, the average distance between adjacent peaks and valleys is not preferably greater than 100 μm. On the other hand, too small a distance may cause significant diffraction of light, affecting the color stability of the dynamic characteristics. A lateral dimension of 5 to 100 μm may be further preferred to be 10 to 30 μm, while producing sufficiently fine features without producing significant diffractive iridescence. The average distance between the peak and the trough in the diffuse reflective curved surface S can be calculated by the following method. Selecting a square area with an area A from the diffuse reflection curved surface S, finding out the number N of wave crests contained in the area A, and considering that the number of the wave crests is basically the same as that of the wave troughs, determining the average distance
In the embodiment of the invention, the diffuse reflection curved surface S is continuous and smooth, namely, the curved surface has no break points and cracks, and meanwhile, the curved surface has no edges and corners. Satisfy the first derivative
Are substantially continuous. For example, from the equation S (x, y) = sin (2 π x/p) x )sin(2πy/p y ) The defined curved surface is continuous and smooth in both x and y directions, P x And P y Are the period in the x and y directions. The actual manufacturing accuracy is of course limited, and the diffuse reflective curved surface S is substantially smooth to achieve the object of the present invention. In addition, the diffuse-reflective curved surface S is not required to be smooth everywhere in practical use, and most of the curved surface with the area of more than 80 percent has smooth characteristics, so that the purpose of the invention can be achieved. The diffusely reflective curved surface S may be periodic in at least one direction, e.g., the diffusely reflective curved surface S may have periodicity in both x and y directions, e.g., a surface determined by the following expression:
S(x,y)＝sin(2πx/p x )sin(2πy/p y )。
wherein p is x Denotes the period in the x direction, p y Indicating the period in the y direction, and x and y represent the arguments.
Of course, it is also possible to have periodicity in only one direction (e.g., the x-direction), such as a curved surface defined by the following expression, which also meets the requirement for smoothness.
S(x,y)＝sin(2πx/p x )。
In general, considering that a function with period P can be decomposed using fourier series, taking a one-dimensional periodic function S (x) as an example,
Conversely, the coefficient C can be set n N, a periodic function can be constructed using the following formula, where N is a positive integer.
For a non-periodic diffuse reflective surface S, a computer program can be used to generate a random height matrix, the values of which represent a plurality of scattered points on the diffuse reflective surface S. By processing the matrix by a certain difference value or blurring, the aperiodic diffuse reflection curved surface SS can be obtained.
The main function of the diffuse-reflective curved surface S is to generate uniform reflected light at a set observation angle set Ω v, similar to the visual impression of diffuse reflection generated by general office paper. For this purpose, the orientation of the individual curved areas is chosen within a continuous set of angles Ω s, which may be defined, for example, in azimuth and elevation. The angle continuum set Ω s is chosen to reflect the incident light uniformly at least into the set of viewing angles Ω v, and thus Ω s has to cover a minimum set determined by the incident light directions ω i and Ω v together. Equivalently, the reflective curved surface S reflects incident light to a set of angles Ω r, which covers the set of viewing angles Ω v, i.e. Ω v is a subset or proper subset of Ω r. In particular, Ω s is designed as the smallest set jointly determined by the incident light directions ω i and Ω v, i.e., Ω v is the same as Ω r. For example, when incident light is normally incident on the element surface, i.e., the element is in the xy plane, the incident light is along the z direction, the azimuth angle of the element of Ω s is the same as the azimuth angle of the element of Ω v according to the law of geometric reflection, and the pitch angle of the element is half of the pitch angle of the element of Ω v.
In order to realize the dynamic characteristics, the diffuse reflective curved surface needs to be modified according to each pixel point of each animation frame, so that the uniform reflected light distribution in the observation angle set Ω v is changed. The size of the diffuse reflection curved surface is larger than the area occupied by all animation frames when the animation frames are presented together, so that each animation frame can correspond to the diffuse reflection curved surface without scaling, and each pixel of a pattern area of the animation frame can find a corresponding position point on the diffuse reflection curved surface, and the position point is modified.
According to the position Pv where the pattern region included in a certain animation frame is located and the observed angle ω v, the position Ps and the angle ω s of the curved surface region to be modified are found, for example, the position and the angle of the curved surface region to be modified can be found for each pixel. In principle, pv and Ps should be at the same position, and ω v, ω s and the incident light angle ω i should satisfy the reflection law of geometric optics, that is, the incident light, the reflected light, and the normal of the curved surface region are in the same plane, and the incident angle is equal to the reflection angle. Here, ω s = f (ω v, ω i) indicates that there is a quantitative relationship between the three, and a specific calculation formula can be found in a general optical textbook, for example, born's optical principle: electromagnetic theory of propagation, interference and diffraction of light. In practical designs, when Pv = Ps, the angle ω s of the curved surface region at this position may not exactly satisfy the geometric reflection law with ω v and ω i. Therefore, the curved surface area can be modified in a certain position range and a certain angle range, namely:
Ps∈(Pv-ΔP,Pv+ΔP)
ωs∈(f(ωv,ωi)-Δω,f(ωv,ωi)+Δω)
the selection of the position deviation delta P and the angle deviation delta omega is specifically determined according to the size of the curved surface area, the resolution of human eyes on angles and sizes and the designed dynamic characteristics, and the principle is that at least one curved surface area to be modified can be found, and the difference which can be distinguished by human eyes is not generated between the curved surface area and the designed pattern. The general positional deviation Δ P is less than 100 μm, preferably less than 50 μm, and the angular deviation Δ ω is defined as the angle between the normal direction of the curved surface region to be modified and the normal direction of the curved surface region corresponding to the preset viewing angle of the pattern, and the angular deviation Δ ω should be less than 3 °, preferably less than 0.5 °.
Generally, let the pitch angles of the two curved surface regions be θ 1 ，θ 2 In azimuth angle of respectively
The angle between the normals of the two curved surface regions can be calculated by the following formula:
in particular implementations, each animation frame may be pixelated, and the diffuse reflective surface may be pixelated. Alternatively, only the pattern region of each animation frame may be pixilated. The essence of pixelation is to divide the animation frame into, for example, nxM small regions, each of which may take up very little area, for example. The small area into which a similar diffusely reflective curved surface is divided after pixelization can also be very small. For example, the width of each small region in the embodiment of the present invention may be 0.5 μm to 10 μm, preferably 2 μm to 4 μm, and correspondingly, the length of each small region may be 0.5 μm to 10 μm, preferably 2 μm to 4 μm.
Further, a first azimuth and a first pitch angle for each animation frame may be determined, each animation frame corresponding one-to-one to a particular viewing angle, whereby the first azimuth and the first pitch angle may be determined based on the viewing angle of the animation frame. In the embodiment of the invention, the observation angle is a direction vector in a rectangular coordinate system. The angle between the direction vector and the xy-plane is defined as the pitch angle (also called the complement angle to the z-axis). And projecting the direction vector onto an xy plane to form a projection vector, wherein the included angle between the projection vector and the x axis is defined as an azimuth angle.
Further, a second azimuth angle and a second pitch angle of each pixel of the diffusely reflective curved surface may be determined, the second azimuth angle and the second pitch angle being determined according to a normal vector at the pixel of the diffusely reflective curved surface. In the diffuse reflection curved surface, the azimuth angle of a pixel can be defined as the included angle between the normal vector of the pixel and the x axis, and the pitch angle can position the included angle between the normal vector of the pixel and the z axis. In an xyz coordinate defined in the embodiment of the present invention, an xy plane is a plane where the optical anti-counterfeit element is located, an x axis may be a longitudinal direction of the optical anti-counterfeit element, a y axis may be a transverse direction of the optical anti-counterfeit element, and a z axis may be an axis perpendicular to the optical anti-counterfeit element.
For each animation frame of the set of animation frames, the following steps may be performed: and searching pixels corresponding to a second azimuth angle and a second pitch angle which are matched with the first azimuth angle and the first pitch angle of the animation frame at the position of the diffuse reflection curved surface corresponding to the pixels of the pattern area in the animation frame, so as to form an area corresponding to the pattern area of the animation frame in the diffuse reflection curved surface. For example, the set of animation frames may be projected perpendicularly onto the diffuse reflective surface in equal proportion, such that a location on the diffuse reflective surface corresponding to each pixel in each animation frame may be determined. Finding pixels corresponding to a second azimuth and second pitch angle that match the first azimuth and first pitch angle of the animation frames may comprise: and searching pixels corresponding to a second azimuth angle of which the angle difference with the first azimuth angle is within a first preset angle difference range and a second pitch angle of which the angle difference with one half of the first pitch angle is within a second preset angle difference range in a preset distance range between the diffuse reflection curved surface and the pixels of the pattern area in the animation frame. Alternatively, in the case of a small pitch angle, the difference in azimuth angle becomes less important. Therefore, in the case where the pitch angle is relatively small, the pixel corresponding to the second pitch angle in which the angular difference between half of the first pitch angle is within the second predetermined angular difference range may be searched only within the predetermined distance range, regardless of the azimuth angle. The preset distance range indicates a distance of less than 100 μm, preferably less than 50 μm, from the position of the pixel of the pattern region in the animation frame. The first predetermined angular difference range is an angular difference of less than 3 °, preferably less than 0.5 °, from the first azimuth angle. The second predetermined angular difference range is an angular difference of less than 3 °, preferably less than 0.5 °, from one half of the first pitch angle. For a pixel of the pattern area, one or more eligible pixels may be found in the diffuse reflective surface, and the one or more eligible pixels may all be modified. After finding pixels in the diffusely reflective curved surface that match each pixel of the pattern area of the animation frame, these matching pixels form an area corresponding to the pattern area of the animation frame. Modifying the area formed in the diffuse reflection curved surface corresponding to the pattern area of each animation frame to form a modified curved surface area.
The secondary structure can be added in the modified curved surface area by modifying the curved surface area, and the characteristic dimension of the secondary structure is obviously smaller than that of the curved surface area, so that the secondary structure can be spread on the surface of the curved surface area along the trend of the curved surface area. The characteristic size of the surface area of a diffusely reflective curved surface may be characterized by the average distance between adjacent peaks and valleys. The secondary structure has a lateral feature size of 0.2 μm to 5 μm and is diffractive or absorptive to visible light. The absorption effect can be realized by the principle of surface plasmon resonance absorption, and the grating structure with the sub-wavelength scale absorbs the incident light with a specific frequency set, so that the color of the reflected light is changed, and the original reflection direction is kept. Generally, when the depth of the sub-wavelength structure is relatively deep, such as 300nm to 700nm, effective absorption can be generated in a wider frequency range, so that the brightness of the reflected light in the direction is significantly reduced, i.e., the sub-wavelength structure becomes an optical absorption or optical black structure.
The modified curved surface region may have the secondary structure as a whole before modification, and provides a specific color or brightness characteristic while generating a uniform reflected light distribution within the viewing angle set Ω v. Thus, the modification of the curved surface region can smooth the modified curved surface region locally or entirely. For example, the secondary structure of the modified curved surface area is removed, so that the secondary structure can generate mirror reflection with higher reflectivity for all visible light bands. Optionally, at least a portion of the unmodified surface region may be provided smooth or with secondary structure.
The modification of the curved surface area can be to flatten the modified curved surface area, so that the modified curved surface area can only reflect the incident light to a specific reverse direction. At other viewing angles, the modified region provides no or only little reflected light, resulting in a darker or darker visual perception than other regions.
The modification of the curved surface region may be adjusting an angle of the modified curved surface region, so that the modified curved surface region reflects all light rays incident to the modified curved surface region to a direction exceeding a preset observation angle set Ω v. The pitch angle of the curved surface region is generally increased beyond a minimum set determined by the incident light directions ω i and Ω v, i.e. the incident light is reflected beyond the set determined by Ω v. The modified curved surface region provides no or little reflected light, resulting in a darker or darker visual perception than other regions.
To create a pattern of sufficient contrast, the surface on which the curved surface region is modified or the surface opposite to the surface on which the curved surface region is modified (e.g., the unmodified curved surface region) may have a plating or coating. This includes reflection enhancing coatings (especially metallized layers), reflection enhancing coatings, reflecting ink layers, absorbing ink layers, coatings of high refractive index materials. The reflection enhancing coating, plating or layer of reflective ink preferably has a color shifting effect, i.e. a change in hue of color at different viewing angles, for example using a fabry perot interference structure. Alternatively, the reflective areas and the curved areas may also be embossed in the reflective ink layer or the absorbing ink layer.
The modification of the curved surface area can be that the modified curved surface area forms a bulge or a recess compared with the peripheral unmodified area; or the curved surface region can be modified by the coating thickness or the plating layer of the modified curved surface region being different from that of the unmodified region. For example, there is a reflective coating, coating or ink on the curved surface areas that are modified, while there is no reflective coating, coating or ink on the curved surface areas that are not modified; or the modified curved surface area is not provided with the reflective plating layer, the coating or the ink, and the unmodified curved surface area is provided with the reflective plating layer, the coating or the ink.
The modification of the curved surface area can be combined and used in a serial mode of the multiple modification modes. For example, a recess lower than the unmodified curved surface region is formed in the modified curved surface region, then a secondary structure is added in the recess, and finally the reflective plating layer of the secondary structure region is removed (i.e., the reflective plating layer has a different thickness from the reflective plating layer of the unmodified curved surface region); or forming a depression lower than the unmodified curved surface area in the modified curved surface area, and filling the depression with color ink, wherein the thickness of the depression is obviously greater than that of the ink in the unmodified curved surface area. The modification of the curved surface area can be combined and used in a parallel mode of a plurality of modification modes. For example, a flat depression is formed in one portion of the modified curved surface region, and a secondary structure is added to another portion of the modified curved surface region along the direction of the curved surface region. The modification of the curved surface region can be a combination of the serial combination mode and the parallel combination mode of the modification modes.
In the embodiment of the present invention, the width of the modified region is 0.5 μm to 20 μm, preferably 2 μm to 10 μm, depending on the visibility of the generated pattern. The modified curved surface area has one or a combination of different reflection colors, different reflection brightness and different reflection textures compared with the unmodified curved surface area.
In the observation angle set omega v of the optical anti-counterfeiting element, the modified curved surface areas are presented as the patterns of the animation frame together, and the unmodified curved surface areas are presented as the background of the animation frame together. The pattern area has a different optical contrast than the background area, and specifically can be one or a combination of different colors, different brightness and different textures visible to human eyes.
Correspondingly, the embodiment of the invention also provides a design method for the optical anti-counterfeiting element, which can comprise the following steps: designing a dynamic feature, wherein the dynamic feature is a group of animation frames visible at a preset observation angle set omega v, and each animation frame comprises a pattern area and a background area forming optical contrast with the pattern area; designing a smooth diffuse-reflectivity curved surface for the optical anti-counterfeiting element, so that incident light can form uniform brightness distribution in a range not less than the preset observation angle set omega v after being reflected by the diffuse-reflectivity curved surface; modifying regions corresponding to the pattern regions of the animation frames to form modified curved surface regions based on the observation angles of the animation frames of the group of animation frames, so that the modified regions and the unmodified curved surface regions have different reflection characteristics, when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface regions jointly represent the patterns of the dynamic features, and the unmodified curved surface regions jointly represent the background of the dynamic features.
The dynamic characteristics can be represented by a group of pictures generated by computer software, such as mathematical computation software, pattern processing software and the like during specific design. For example, using a bitmap in the format bmp, different colored design patterns and a common background of the patterns are represented by gray values of 0-255. Each picture corresponds to visual information presented to human eyes under a specific observation angle, and is called a frame of animation of designed dynamic characteristics. The specific working principle and benefits of the design method for an optical anti-counterfeiting element according to the embodiment of the present invention can refer to the description of the optical anti-counterfeiting element according to the embodiment of the present invention, and will not be described herein again.
Correspondingly, the embodiment of the invention also provides an anti-counterfeiting product using the optical anti-counterfeiting element in any embodiment of the invention. The security product may be in the form of, for example, a security thread, a security strip, a security label, or the like. Embodiments of the present invention further provide a data carrier with a security element according to any of the embodiments of the present invention or a security product according to any of the embodiments of the present invention, which can be arranged in an opaque area of the data carrier and in or above a transparent window area or through-opening in the data carrier. The data carrier can be, in particular, a value document, for example a banknote (in particular a paper banknote, a polymer banknote or a film composite banknote), a stock certificate, a ticket, a check, a high-value admission ticket, but also an identification card, for example a credit card, a bank card, a cash card, an authorization card, a personal identification card, or a personal information page of a passport, etc.
The optical anti-counterfeiting element and the manufacturing method thereof provided by the invention in real time are further described below with reference to the attached drawings.
Fig. 1 is a schematic diagram of diffuse reflection action of a diffuse reflection curved surface area of an optical anti-counterfeiting element on incident light. The plane of the optical anti-counterfeiting element 1 is defined as xy plane, and the diffuse reflection curved surface S is composed of a plurality of smoothly connected curved surface areas 3. Smooth joining in the present embodiment means that the first derivative of the two faces being joined is continuous, i.e. there is no joint but there is no break and no edge. The curved surface region 3 can have projections and depressions. In fig. 1, the optical security element is provided with a substrate 6, the diffusely reflective curved surface S being located on one side of the substrate. The presence of the substrate 6 is however a requirement of the processing process, which may not be part of the optical security element itself. The substrate 6 may be part of a security product formed by the optical security element 1. Of course, the substrate can also be removed in a security product, for example a hot stamped product, the structured layer being transferred to another carrier, without the substrate 6 forming part of the security product. The substrate 6 does not form an essential component of the optical security element 1. The incident light 4 is incident on one side of the substrate with the diffuse reflection curved surface, and the incident light 4 forms a plurality of reflected light rays 5 in different directions through the reflection action of the diffuse reflection curved surface S. By controlling the angular distribution of the plurality of curved surface areas 3, which angles are defined by, for example, azimuth and elevation angles, a substantially uniform diffuse reflective visual effect covers a predetermined set of viewing angles Ω v of the animated feature. For simplicity of description without loss of generality, the direction of the incident light 4 is set to the z direction, which is a direction perpendicular to the xy plane. While the azimuth angle of the elements of the set Ω v is predetermined to be 0-360 ° and the pitch angle is predetermined to be 0-35 °. Accordingly, the average distance between the peaks and the valleys of the diffusely reflective curved surface can be controlled within a range of 20 μm to 50 μm while the vertical height is set to 0 μm to 10 μm, so that the incident light 4 is reflected by the diffusely reflective curved surface S to the angle set Ω r, which can cover the observation angle set Ω v. Since a finite number is usually used to represent a continuous surface in practical design, the coverage of the present invention specifically means that any element in the set Ω v can find a corresponding element close enough to it in Ω r, for example, the included angle between the two is not more than 1 °. In practical design, the smooth reflective curved surface should at least include 3000 peaks and valleys, preferably more than 50000 peaks and valleys, so as to generate a sufficiently fine and uniform reflected light distribution. Fig. 1 is only a diagram showing that the diffuse reflection curved surface of the optical anti-counterfeiting element can generate diffuse reflection effect on incident light, and the specific dynamic characteristics and the modification mode of the curved surface area are not involved.
To further illustrate the specific form that the diffusely reflective curved surface S may take, fig. 2 illustrates a periodic diffusely reflective curved surface design. An analytical equation is adopted:
S(x,y)＝sin(2πx/p x )+sin(2πy/p x )+3 sin(2πx/p x )sin(2πy/p y )
where Px and Py are periods in the x and y directions, px =20 μm and Py =30 μm may be set. This formula produces a smooth diffuse curved surface with periodicity in both the x and y directions. The pitch angle of each area of the diffuse reflection curved surface can be integrally adjusted by adjusting the overall fluctuation height of the diffuse reflection curved surface S according to the requirement. Both sine and cosine functions are infinitely derivable, so that the equation S (x, y) fully satisfies the requirements of continuity and smoothness. Let F (x, y, z) = z-S (x, y) =0, and any pixel point (x, y) on the curved surface S 0 ,y 0 ,z 0 ) Normal equation and normal vector of
Can be calculated by the following formula respectively:
(x-x 0 )/F x (x 0 ,y 0 ,z 0 )＝(y-y 0 )/F y (x 0 ,y 0 ,z 0 )＝(z-z 0 )/F z (x 0 ,y 0 ,z 0 )
here, fx denotes a first derivative of the function F (x, y, z) with respect to x, fy denotes a first derivative of the function F (x, y, z) with respect to y, and Fz denotes a first derivative of the function F (x, y, z) with respect to z.
Can directly obtain (x) through a normal vector 0 ,y 0 ,z 0 ) Azimuth angle phi (defined as the angle between the normal vector and the x axis) and pitch angle theta (defined as the angle between the normal vector and the z axis) of the curved surface region:
tan(φ)＝F y /F x |(x 0 ,y 0 ,z 0 )。
FIG. 3 illustrates an aperiodic diffusely reflective curved surface design. For a non-periodic diffuse reflective surface S, one method is to generate a matrix random height matrix using a computer program, the values of which represent a number of scatter points on the surface S. By processing the matrix by a certain difference value or blurring, the aperiodic diffuse reflection curved surface S can be obtained. The difference processing may use bilinear interpolation, resampling using pixel region relations, bicubic interpolation of 4x4 pixel neighborhoods, or Lanczos interpolation of 8x8 pixel neighborhoods, etc., while the blur processing may use average blur, defocus blur, motion blur, or gaussian blur, etc. The use of difference processing or blurring ensures that there are no sharp transitions and breaks between the heights, and thus ensures the smooth nature of the diffuse surface, i.e., the first derivative is substantially continuous. Random height may be generated using pseudo-random numbers, which are strings of numbers that appear random but are computed by deterministic algorithms, and thus, in the strict sense, they are not true random numbers. However, pseudo-random numbers are widely used because pseudo-randomly chosen statistical properties (such as equal probability of individual numbers or statistical independence of successive numbers) are generally sufficient for practical purposes, and unlike true random numbers, pseudo-random numbers are easy to generate by computers.
According to the animation frames forming the dynamic characteristics, the specific curved surface area of the reflection area of the diffuse reflection is modified, so that the reflection characteristics of local difference are generated. Setting the incident ray angle ω i to be along the z-axis, FIGS. 4 and 5 provide two examples of how to determine the region of the curved surface to be modified.
FIG. 4 is an embodiment of determining the area of a surface to be modified based on an animation frame. The two tables of fig. 4 represent the pitch and azimuth angles, respectively, of the local surface area. Because the sampling density of the discrete data is limited, the data of the pitch angle and the azimuth angle in fig. 4 do not obviously reflect the smooth characteristic of the diffuse reflection curved surface S, which does not affect the principle description of how to determine the curved surface area to be modified by using the animation frame in this embodiment.
An animation frame of the described animated feature is defined as being observed in the pitch =0 ° and azimuth =0 ° directions. 71 is the pattern area of the animation frame and 72 is the background area of the animation frame. 71 and 72 have an optical contrast visible to the human eye. The size of the reflection area 21 corresponding to the animation frame 7 on the diffuse reflection curved surface S is not smaller than at least the size of the area where the animation frame 7 is located, so that the visual information of the animation frame 7 can be presented completely. Taking an arbitrary point Pv (which may be considered as an arbitrary pixel point) on the pattern region 71 as an example, a corresponding point of Pv is determined in the reflection region 2. In the reflection area 21, a curved surface area where the pitch angle =0 ° or the deviation therefrom is smaller than Δ ω is sought within the range of Δ P with Pv as the center point. In the case of a small pitch angle, the difference in azimuth angle becomes less important, so the azimuth angle is not taken into account here. By appropriately controlling the magnitudes of Δ P and Δ ω, it is always possible to find a point corresponding to any one point Pv in the reflection area 21, i.e., to find a curved surface area to be modified. For example, the average distance between the adjacent peaks and valleys of the curved surface region is 30 μm, Δ P =60 μm, Δ ω =1 °, and a point (0.4 °,75.2 °) can be found in the reflective region 2 at the lower right of the Pv point, and the modification of the curved surface region corresponding to the point can produce the expected visual contrast at the Pv point of the animation frame 7.
FIG. 5 is another embodiment of determining a region of a surface to be modified based on an animation frame. The two tables of fig. 5 represent the pitch and azimuth angles, respectively, of the local surface area. Because the sampling density of the discrete data is limited, the data of the pitch angle and the azimuth angle in fig. 5 do not obviously reflect the smooth characteristic of the curved surface S, which does not affect the principle description of how to determine the curved surface region to be modified by using the animation frame in this embodiment.
In the animation frame 8, 81 is a pattern region of the animation frame 8, and 82 is a background region of the animation frame 8. The pattern area 81 has an optical contrast visible to the human eye with the background area 82. The pattern region 81 has a positional change with respect to the pattern region 71, and the moving image frame 8 is defined to be observed in a direction of a pitch angle =20 ° and an azimuth angle =90 °. The size of the reflection region 22 corresponding to the animation frame 8 on the diffuse reflection curved surface S is at least not smaller than the size of the region where the animation frame 8 is located, so that the visual information of the animation frame 8 can be completely presented. Taking an arbitrary point Pw (which may be considered as an arbitrary pixel) on the pattern region 81 as an example, a corresponding point Pw is determined in the reflective region 22. In the reflection region 22, a curved surface region which is the same as or has an angular deviation smaller than Δ ω as a curved surface region determined by an angle (pitch =10 ° and azimuth =90 °) is searched for within a range of Δ P with Pw as a center point. By appropriately controlling the magnitudes of Δ P and Δ ω, the curved surface region to be modified can always be found in the reflection region 22. For example, the average distance between the peaks and valleys adjacent to the curved surface region is 30 μm, Δ P =60 μm, Δ ω =1 °, and points (10.1 °,92.2 °), (9.8 °,89.7 °) can be found in the vicinity of the Pw point in the reflection region 22, and the modification of the curved surface region corresponding to each of the two points can generate the predicted visual contrast at the Pw point of the animation frame 8.
The modification of the curved surface region can be done in a number of ways. The modified curved surface region 31 of fig. 6 is modified in a particular manner, either partially or entirely, to produce a different reflection characteristic than the unmodified curved surface region 32. 9 is an example of a modification. Wherein:
and 91, modifying the curved surface region is to form a recess in the periphery (e.g., the unmodified curved surface region) of the modified curved surface region, wherein the depth of the recess is selected from 0.5 μm to 3 μm, and is related to the width of the modified region. Meanwhile, the modified curved surface area can be flattened, so that the modified curved surface area can only reflect incident light to a specific reverse direction, and under other observation angles, the modified curved surface area does not provide or only provides little reflected light, so that darker or darker visual perception is generated compared with other areas.
92, the modification of the curved surface area may add a secondary structure to the modified area, the secondary structure having a characteristic dimension significantly smaller than the dimension of the curved surface area, and thus may be spread over the surface of the curved surface area in the direction of the curved surface area. The secondary structure has a lateral feature size of 0.2 μm to 5 μm and is diffractive or absorptive to visible light. The absorption effect can be realized by the principle of surface plasmon resonance absorption, and the grating structure with the sub-wavelength scale absorbs the incident light with a specific frequency set, so that the color of the reflected light is changed, and the original reflection direction is kept. Generally, when the depth of the sub-wavelength structure is relatively deep, such as 300nm to 700nm, effective absorption can be generated in a wider frequency range, so that the brightness of the reflected light in the direction is significantly reduced, i.e., the sub-wavelength structure becomes an optical absorption or optical black structure.
93 to et al, the curved surface region to be modified may be integrally provided with said secondary structure prior to modification, while providing a uniform reflected light distribution within the set of viewing angles Ω v, and while providing specific color or brightness characteristics. Therefore, the modification of the curved surface area can smooth the modified curved surface area, i.e. remove the secondary structure of the curved surface area to be modified, so that the secondary structure can generate mirror reflection with higher reflectivity for all bands of visible light.
94 is shown as a pattern that produces sufficient contrast, the surface on which the curved surface region is modified or the surface opposite the surface on which the curved surface region is modified (e.g., the unmodified curved surface region) may have a plating or coating. This includes reflection enhancing coatings (especially metallized layers), reflection enhancing coatings, reflecting ink layers, absorbing ink layers, coatings of high refractive index materials. The reflection enhancing coating, coating or layer of reflective ink preferably has a color shifting effect, i.e. a change in hue of color at different viewing angles, for example by means of a Fabry-Perot interference structure, e.g. Cr (5 nm)/MgF 2 (500 nm)/Al (50 nm) structure. Alternatively, the reflective areas and the curved areas may also be embossed in the reflective ink layer or the absorbing ink layer.
The curved surface region can be modified by the coating thickness or the plating layer of the modified curved surface region being different from that of the unmodified curved surface region. For example, there is a reflective coating, coating or ink on the curved surface areas that are modified, while there is no reflective coating, coating or ink on the curved surface areas that are not modified; or there is no reflective coating, layer or ink on the curved surface area that is modified, while there is reflective coating, layer or ink on the curved surface area that is not modified.
95, the modification of the curved surface region may be adjusting the angle of the modified curved surface region, so as to reflect the incident light to the direction exceeding the preset observation angle set Ω v. The pitch angle of the curved surface region is generally increased beyond a minimum set determined by the incident light directions ω i and Ω v, i.e. the incident light is reflected beyond the set determined by Ω v. The modified curved surface region provides no or little reflected light, resulting in a darker or darker visual perception than other regions.
96 indicates that the modification of the curved surface region can be combined in a serial manner of a plurality of modification modes. For example, a recess lower than the peripheral region is formed in the modified curved surface region, then a secondary structure is added in the recess, and finally the reflective plating layer in the secondary structure region is removed (i.e., the thickness of the reflective plating layer is different from that of the unmodified curved surface region); or forming a depression lower than the peripheral area in the modified curved surface area, and filling color ink in the depression, wherein the thickness of the depression is obviously greater than that of the ink in the unmodified curved surface area.
97 indicates that the modification of the curved surface region can be combined in a parallel manner of a plurality of modification methods. For example, a flat depression is formed in one portion of the modified curved surface region, and a secondary structure is added to another portion of the modified curved surface region along the direction of the curved surface region. The modification of the curved surface area can be a combination of the serial combination mode and the parallel combination mode of the modification modes.
The modified portion may be present in part or in the entirety of the modified curved surface region. For an ideal planar curved surface region, the modified portion would be equal to the modified curved surface region. And for curved surface regions, the modified portion will be present in a part of the modified surface region. The width of the modified region is 0.5 μm to 10 μm, preferably 2 μm to 4 μm. The modified curved surface area has one or a combination of different reflection colors, different reflection brightness and different reflection textures compared with the unmodified curved surface area.
A portion of the curved areas 31 and 32 of the diffusely reflective curved surface S in fig. 6 reflects the incident light 4 into directions 51 and 52, respectively. The reflected light of the modified curved surface area 31 generates a pattern of an animation frame, i.e. the modified curved surface areas are presented as the pattern of the animation frame together; the reflected light rays of the unmodified curved surface regions 32 generate the background of the animation frame, i.e. the unmodified curved surface regions collectively appear as the background of the animation frame. The pattern area has a different optical contrast than the background area, and specifically can be one or a combination of different colors, different brightness and different textures visible to human eyes.
Fig. 7 shows a schematic representation of a banknote 10, which banknote 10 has an optical security element according to the invention, which is embedded in the banknote 10 in the form of a window security thread 101. In addition, the optical anti-counterfeiting element can be used in a labeling mode 102, and an opening area 103 can be formed in the banknote substrate 10, so that the banknote substrate can be observed in a light-transmitting mode conveniently. It will be appreciated that the invention is not limited to security threads and banknotes but may be used in a variety of security products, for example in labels on goods and packaging, or in security documents, identity cards, passports, credit cards, health care cards and the like. In banknotes and similar documents, in addition to security threads and labels, it is also possible to use, for example, wider security strips or transfer elements.
An embodiment of the present invention provides a storage medium, on which a program is stored, where the program is executed by a processor to implement the design method for an optical anti-counterfeiting element according to any embodiment of the present invention.
The embodiment of the invention provides a processor, wherein the processor is used for running a program, and the program is used for executing the design method for the optical anti-counterfeiting element according to any embodiment of the invention when running.
The embodiment of the invention provides electronic equipment, which comprises a processor, a memory and a program which is stored on the memory and can run on the processor, wherein the processor executes the program to realize the design method for the optical anti-counterfeiting element in any embodiment of the invention.
The present application also provides a computer program product adapted to perform a program for initializing the steps of the method for designing an optical security element according to any of the embodiments of the present invention when executed on a data processing device.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In a typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.
The memory may include forms of volatile memory in a computer readable medium, random Access Memory (RAM) and/or non-volatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). The memory is an example of a computer-readable medium.
Computer-readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.
The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art to which the present application pertains. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (24)
1. An optical security element capable of presenting a dynamic feature, said dynamic feature being pre-designed as a reproduction of a set of animated frames visible at a set of preset viewing angles Ω v, said animated frames comprising a pattern region and a background region forming an optical contrast with said pattern region;
the optical anti-counterfeiting element is provided with a smooth diffuse-reflectivity curved surface, and incident light forms uniform brightness distribution in a range not less than the preset observation angle set omega v after being reflected by the diffuse-reflectivity curved surface;
the diffuse reflection curved surface comprises a modified curved surface area and an unmodified curved surface area, the modified curved surface area and the unmodified curved surface area have different reflection characteristics, and the modified curved surface area corresponds to the pattern area;
when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface areas jointly represent the pattern of the dynamic feature, and the unmodified curved surface areas jointly represent the background of the dynamic feature.
2. An optical security element according to claim 1, wherein the diffusely reflective curved surface is periodic in at least one direction.
3. An optical security element according to claim 1, wherein the diffusely reflective curved surface is non-periodic in at least one direction.
4. An optical security element according to claim 1, wherein the average distance between adjacent peaks and troughs of the diffusely reflective curved surface is from 5 μm to 100 μm, preferably from 10 μm to 30 μm.
5. An optical security element according to claim 1, wherein the average height difference between adjacent peaks and troughs of the diffusely reflective curved surface is from 1 μm to 10 μm.
6. An optical security element according to claim 1, wherein at least a portion of the unmodified areas are smooth or have a secondary structure.
7. An optical security element according to claim 1, wherein the modified region is modified by one or more of the following:
adding a secondary structure to the modified region;
smoothing the modified region;
flattening the modified area;
arranging the modified region to have a protrusion or a depression compared to the unmodified region;
adjusting the angle of the modified region so that the incident light is reflected to a range beyond the preset set of viewing angles Ω v; or alternatively
The thickness of the plating or coating of the modified region is adjusted to be different from the unmodified region.
8. An optical security element according to claim 7, wherein where the modified regions are modified by two or more of the plurality of means, the two or more means are present in a parallel combination and/or a serial combination.
9. An optical security element according to any one of claims 6 to 8, wherein the secondary structures have a lateral feature size of from 0.2 μm to 5 μm.
10. An optical security element according to claim 1, wherein the modified regions have a width of 0.5 μm to 20 μm, preferably 2 μm to 10 μm.
11. An optical security element according to claim 1, wherein the different reflection characteristics are that the modified region and the unmodified region have one or a combination of different reflection colors, different reflection brightness, or different reflection textures when irradiated by the incident light.
12. A method of designing an optical security element, the method comprising:
designing a dynamic characteristic which is the reproduction of a group of animation frames visible at a preset observation angle set omega v, wherein each animation frame comprises a pattern area and a background area forming optical contrast with the pattern area;
designing a smooth diffuse-reflectivity curved surface for the optical anti-counterfeiting element, so that incident light can form uniform brightness distribution in a range not less than the preset observation angle set omega v after being reflected by the diffuse-reflectivity curved surface;
modifying a region corresponding to the pattern region of each animation frame of the set of animation frames based on an observation angle of each animation frame to form a modified curved surface region such that the modified region has a different reflection characteristic from an unmodified curved surface region,
when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface areas jointly represent the pattern of the dynamic feature, and the unmodified curved surface areas jointly represent the background of the dynamic feature.
13. The method of claim 12, wherein the diffusely reflective curved surface is periodic in at least one direction.
14. The method of claim 12, wherein the diffuse reflective curved surface is non-periodic in at least one direction.
15. Method according to claim 12, wherein the average distance between adjacent peaks and troughs of the diffusely reflective curved surface is from 5 μm to 100 μm, preferably from 10 μm to 30 μm.
16. The method of claim 12, wherein the average height difference between adjacent peaks and valleys of the diffusely reflective curved surface is from 1 μ ι η to 10 μ ι η.
17. The method of claim 12, wherein modifying the region corresponding to the pattern region of each animation frame of the set of animation frames to form a modified surface region based on a viewing angle of each animation frame comprises:
pixelating each animation frame of the set of animation frames and the diffuse reflective surface;
determining a first azimuth angle and a first pitch angle of each animation frame, the first azimuth angle and the first pitch angle being determined according to an observation angle of the animation frame;
determining a second azimuth angle and a second pitch angle of each pixel of the diffuse reflectivity curved surface, wherein the second azimuth angle and the second pitch angle are determined according to a normal vector of the pixel of the diffuse reflectivity curved surface;
for each animation frame of the set of animation frames, performing the steps of:
finding pixels corresponding to a second azimuth angle and a second pitch angle that match the first azimuth angle and the first pitch angle of the animation frame at positions of the diffusely reflective curved surface corresponding to pixels of the pattern region in the animation frame, thereby forming a region corresponding to the pattern region of the animation frame in the diffusely reflective curved surface; and
modifying an area formed in the diffuse reflective curved surface corresponding to a pattern area of the animation frame.
18. The method of claim 17, wherein finding pixels corresponding to a second azimuth angle and a second pitch angle that match the first azimuth angle and the first pitch angle of the pixels of the pattern region at a location of the diffuse reflective curved surface corresponding to the pixels of the pattern region in the animation frame comprises:
and searching pixels corresponding to a second azimuth angle of which the angle difference with the first azimuth angle is within a first preset angle difference range and a second pitch angle of which the angle difference with one half of the first pitch angle is within a second preset angle difference range in a preset distance range between the diffuse reflection curved surface and the pixels of the pattern area in the animation frame.
19. The method of claim 18,
the preset distance range indicates that the distance between the position of the pixel of the pattern area in the animation frame and the position of the pixel is less than 100 μm, preferably less than 50 μm; and/or
The first preset angle difference range means that the angle difference between the first azimuth angle and the first preset angle difference range is less than 3 degrees, and preferably less than 0.5 degrees; and/or
Said second predetermined angular difference range means an angular difference of less than 3 °, preferably less than 0.5 °, from said first pitch angle.
20. The method of claim 12 or 17, wherein modifying the region corresponding to the pattern region of each animation frame to form a modified surface region comprises performing one or more of:
adding a secondary structure to the modified region;
smoothing the modified region;
flattening the modified area;
arranging the modified region to have a protrusion or a depression compared to the unmodified region;
adjusting the angle of the modified area so that the incident light is reflected to a range beyond the preset observation angle set omega v; or alternatively
The thickness of the plating or coating of the modified region is adjusted to be different from the unmodified region.
21. The method of claim 12,
the dynamic characteristics are one or a combination of translation, rotation, scaling, deformation, hiding and yin-yang conversion; and/or
The optical contrast is one or the combination of different colors, different brightness and different texture which can be seen by human eyes.
22. The method according to claim 12, wherein the modified region has a width of 0.5 to 20 μm, preferably 2 to 10 μm.
23. A security product using the optical security element according to any one of claims 1 to 11.
24. A data carrier, characterized in that it has an optical security element according to any one of claims 1 to 11 or a security product according to claim 23.
Priority Applications (3)
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| CN202110449712.1A CN115230363B (en) | 2021-04-25 | 2021-04-25 | Optical anti-counterfeiting element, design method thereof and anti-counterfeiting product |
| EP22794222.4A EP4331857A1 (en) | 2021-04-25 | 2022-01-25 | Optical anti-counterfeiting element, design method therefor, and anti-counterfeiting product |
| PCT/CN2022/073790 WO2022227741A1 (en) | 2021-04-25 | 2022-01-25 | Optical anti-counterfeiting element, design method therefor, and anti-counterfeiting product |
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| CN202110449712.1A CN115230363B (en) | 2021-04-25 | 2021-04-25 | Optical anti-counterfeiting element, design method thereof and anti-counterfeiting product |
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| EP (1) | EP4331857A1 (en) |
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| Publication number | Publication date |
|---|---|
| EP4331857A1 (en) | 2024-03-06 |
| WO2022227741A1 (en) | 2022-11-03 |
| CN115230363B (en) | 2024-03-29 |
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